Signaling



April 9, 1935. H. cHlRElx 1,997,042

' SIGNALING Filed Deo. 18', 1951 :EE-L+ ATTORNEY Patented Apr. 9, v1935 VSTVATS l, u SIGNALING Y Y :Henri Chjreiii,V Paris,- France, assigner to C0111-` l i. l pagn'ie GeneraleDe Telegraphie Sans Fil, Paris,

, .France ,a corporation of France 4flpplication.,December"18,1931, Serial No. 581,811 Y In France December 27, 1930 l f 2 claims. l (c1. 173-44) 'hepresentinvention relates toav method of signaling which-utilizes a method of and apparatus for obtaining' atranspositionof frequencies.

The term `transp'osition,"` as it 'isuniversally usedjandas employedfherein denotes 4the dis` placement cfa frequency spectrum by,` a `fixed Y sage signals cfa transposed spectrtun'tby the addl0 frequency; in` other words, the obtainingfrorn an original frequency spectrum comprising the mes'- ing or `deducting lofa predetermined frequency I from each 'frequency of theoriginal spectrum.

The present inventionfjwhich obtains'thfis result nds particular application multiplexfteleandinisecret-signalingsystems, operatingl `on a code basis or any other suitable basisf ,"1

`As will'appear more clearly lfiereinafter,"infacie cordance withl the present invention,` the message Waves are fed-'into the input end of the: system and at the Youtput end-there".isobtained a specf tru'm displaced: or 'shifted' in the frequency band,

which mode of operationfrenders the shifted spectrum entirely unintelligible if it Vwere received siredL `may vbe transmitted simultaneouslyl with other message waves; utilizing theoriginal 'spec trum, thusrconstituting'a multiplex system.`

`More specifically the presentlr inv'entioncorn` prises an improvement on my Patent No. 1,946,- 274, vgranted February 6, 19%,` to which reference v is made. Particularly,` fthis invention is an -iin-f provement onthe circuit. arrangement illustrated in Figure 7 of thejdrawings of mypatent mentioned above.:` Essentially, Patent No.,1,946,27fl, supra," describes an varrangementf for obtaining .the transpositionof 'af-frequency"spectrum, and this vis accomplished therein by first subjecting the givenjspectrum to a phase displacement of ninetydegrees in order to obtain in the phase `displaced spectrum the same' amplitude relations of the currents of special frequencies as in the original spectrum. Then, each of' the two spectra l areimpressed respectively, on a diagonal of in- -dividual bridges comprising two rotatable condensers for adjacent legs, periodically variable with the frequency of transposition, and for the other two legs two othergcondenserswhose values are very much different from those of the variable condensers. The two individual bridges are each joined at anapex belonging tothe second diagonal of the bridges andthe transposed spectrum is collected at the apices `of the bridges opposite this common orrjointapex.

An object of thenpre's'eur invention consists inV vg presenting `a diagram of the bridges, analytically equivalent to the one which has just been described. l g Y Y Another object oftliefpresent invention is to provide an arrangement wherein the bridge, laccording to the first object, is utilized forthe transposition of a spectrum of frequencies obtainedY from a modulatedwave Yby the use of .fil-

ters. l graphl andftelephone'communication systems, l

A better understanding of the present invention maybe had by referring Vtothe accompanying drawing, wherein Figure l illustrates oneem- Vloodiment of the present invention, and Figure 2 vquencies supplyVv spectra of frequencies which are lmutually in quadrature" with respect to each other, andmay be obtained, if desired, asvdis clsedV in my patent,A supra. TheV secondary windings taken as a whole ofY these transformers areV each closed uponV twoidenti'cal 'condensers C1, C'i, C2, and Cz whiohare periodically variable atthe transposition frequency. In eachl of the groups one of the condensers increases while the other one diminishes and theactions are phasedisplaced vby an amount equal-to 1r/2 in:one group with reference to the other. The midpoint of each of these'groups may advantageously, though not necessarily, be connected with the ground (G, G') and the output potential is fed for each of these groups between the midpoint of the seo-V ,ondaries of the transformers and the ground to the terminals of fixed condensers K1, K2, whoseV capacity should be high compared with that of the variable part or member of the periodical variation condensers. Analytically, this arrangementis equivalent to the circuit shown in FigureY 7 of the drawings of my parent Patent No. 1,946,-v

274 granted February 6, 1934. Y f

'Ihe transposed frequency will be obtainable again between the output terminals Y and Z.

The theory underlying the above invention is as follows: Y l

Let us designate by n a cos (Slut-wn) the spectrum furnished by the source at A.

Let us designate by n an sin (Unt- Son) the spectrum furnished by source N at B. lLet us designate by i1 the current flowing rthrough condenser C1 (Figure 1). I Let us designate by i2 the current flowing jaar; fade i* ffgdf Y By substitution there follows this:

cos wt A or else I v Y n Y Vyg=fi an cos (Slut-@J cos wt C0 o .Y

Similarly there is obtained c n Y VZG=- Y an sin (mt-a) sin wt Co; :o Addition of these two potentials results in c n v VYZ=VYG+VZG=E an c0S{(Qn-w)t"i9n} 0 0 In other words, a spectrum that has been transposed by an amount equal to the fixed frequency w compared with the original spectrumv n Y a7l cos @nt-ga). 0

If recourse is to be had to filters in order to separate the frequencies either in aggregation or difference it is possible to use the scheme in Figure` l reduced to one-half as shown again in Figure 2. It will be seenthat-there has been providcdinthis illustration a regulating potentiometer P in order to facilitate the work of ascertaining the point of equilibrium in the case where the periodic condensers should happen to be dissimilar.

Y The circuit schemes shown in Figures 1 and 2, especially when recourse. is had to rotary condensers, are ableto define or X the potential dif ference between the rotors and the ground and `to thus facilitatethe practical application of the scheme. Y

What Iclaim is; 1.'A frequency transposition system for obv taining a transposed frequency spectrum in a communication lsystem having, inA combination, an audio frequency transformer-comprising primary and secondary windings, another audio frequency transformer comprising primary and secondary windings, two sources of oscillations havving spectra of frequencies which are mutually in quadrature but which possess the same amplitude relations, each of said .primaryk windings beingarranged Vto be connected1 respectively to one' of said sources, an output circuit, connec- -tions from thel midpoint of the secondary Ywindings of `each of said transformers to the output circuit, connections from both sides of both of saidfsecondary windings to ground, and capacity l elements `serially connected insaid ground cond nections, said capacity elements being rotatable at a predetermined xed frequency whereby the` output circuit furnishes a'transposed spectrum whose frequencies differ fromthe input spectrum frequencies by the amount of the fixed frequency. i .Y l

2. A system of the'type described in claim l, characterized in this, that, the midpoints of the secondary windings of both audio lfrequency transformers are connected to ground through capacity elements.,

HENRI CHIREIX. 

